1. Field of the Invention
The present invention relates to technologies relating to polishing pads used in, for example, the CMP method (chemical-mechanical polishing method), and, in particular, relates to a method for manufacturing grooved polishing pads wherein a multiple grooves are formed on the front surface and/or back surface thereof in order to increase the polishing precision.
2. Description of the Related Art
Conventionally, technologies have been known for polishing processes for high precision polishing of objects using polishing pads in the form of thin disks of synthetic resin materials. For example, in recent years there has been a great deal of interest in providing technologies for performing CMP of semiconductor wafers and devices with multilayer structures such as conductive layers on the surface of semiconductor layers. In particular, given increases in the density of the electronic components to be polished, there is the need for greater precision and greater efficiency polishing processes, and in CMP in particular. There have been reports of not only improvement in polishing devices, slurries, polishing pad materials, and so forth, to this end, but also reports of the effectiveness of forming grooves of the appropriate shapes on the front and or back surfaces of the polishing pads.
These types of polishing pads used in CMP are conventionally made from synthetic resin materials, and, typically, the grooves of appropriate shapes are molded at the same time as the fabrication of the polishing pads. However, given the increasingly rigorous requirements for polishing precision, the present inventors, aware of the limitations in the fabrication of grooves using molding, have been the first to propose the fabrication of grooves using a cutting (machining) process. Moreover, in this type of cutting of grooves, typically a large number of grooves adjacent one another in parallel are cut simultaneously through a multi-edged tool that is equipped with a plurality of blade edge parts arranged in parallel to one another in order to raise the efficiency of the machining cycle.
However, in order to achieve high precision polishing, as well as in order to achieve effective cutting with respect to a soft polishing pad, it is desirable to form a large number of grooves with a small pitch and a small width onto a surface of the polishing pad, as pointed out in the previous application by the present inventors. In particular, the groove widths and groove pitches have been miniaturized to their limits in order to respond to recent requirements for high levels of high precision polishing performance.
At this point, in machining of polishing pads using conventional multi-edged tools, the gaps between the individual blade edge parts provided in the multi-edged tools have become narrow due to the narrowing of the desired groove pitch. Because of this, the frictional heating that occurs repetitively in the blade edge parts due to the friction with the polishing pads is concentrated on the narrow parts positioned between the blade edge parts in the polishing pads, with the risk of causing problems such as thermal deformation of the polishing pads, which are made from synthetic resin.
Further, the narrower gaps between the individual blade edge parts will cause low air flows flowing through the gaps. This may cause deterioration in cooling performance by means of the air flows flowing through the gaps, thereby enhancing the risk of the heating problems. In order to address the heating problems, the cutting speed must be decreased, thereby lowering the machining rate.
Moreover, where the individual blade edge parts make small in the width length and the gap distance, manufacturing of the blade edge parts becomes difficult, and defects or dimensional errors of the blade edge parts may occur readily.
In addition, the narrower gaps between the individual blade edge parts may readily cause the sticking of the cutting parts against the gaps. This may further deteriorate air flows through the gaps between the individual blades, so that the resultant insufficient cooling may cause additional problems. The cutting parts stuck to gaps between adjacent blade edge parts may be welded due to the heat of the blade edge parts, thereby ragging the cutting surfaces of the grooves, leading readily to deterioration in cutting accuracy of the grooves.